Update script for dynv6.com to set your IPv4 address and IPv6 prefix

dynv6.sh

#!/bin/sh -e
hostname=$1
device=$2
file=$HOME/.dynv6.addr6
[ -e $file ] && old=`cat $file`

if [ -z "$hostname" -o -z "$token" ]; then
  echo "Usage: token=<your-authentication-token> [netmask=64] $0 your-name.dynv6.net [device]"
  exit 1
fi

if [ -z "$netmask" ]; then
  netmask=128
fi

if [ -n "$device" ]; then
  device="dev $device"
fi
address=$(ip -6 addr list scope global $device | grep -v " fd" | sed -n 's/.*inet6 \([0-9a-f:]\+\).*/\1/p' | head -n 1)

if [ -e /usr/bin/curl ]; then
  bin="curl -fsS"
elif [ -e /usr/bin/wget ]; then
  bin="wget -O-"
else
  echo "neither curl nor wget found"
  exit 1
fi

if [ -z "$address" ]; then
  echo "no IPv6 address found"
  exit 1
fi

# address with netmask
current=$address/$netmask

if [ "$old" = "$current" ]; then
  echo "IPv6 address unchanged"
  exit
fi

# send addresses to dynv6
$bin "http://dynv6.com/api/update?hostname=$hostname&ipv6=$current&token=$token"
$bin "http://ipv4.dynv6.com/api/update?hostname=$hostname&ipv4=auto&token=$token"

# save current address
echo $current > $file

Made my shell script like this. Think it's leightweight and easy to read

#!/bin/bash

# dynDNS with dynV6 & ipv6 done right

# Initial values

newIpV6=$(ip -6 addr show scope global | grep inet6 | sed -e 's/^.*inet6 \([^ ]*\)\/.*$/\1/;t;d')
oldIpV6='No data in cachefile'

# Change these parameters as you want to

logfile=~/dynv6.log
cachefile=~/.dynv6cache
token=<your-token>
zone=<your-zone>

if [[ -f $cachefile ]]; then
    oldIpV6=$(cat $cachefile)
fi

if [[ $newIpV6 != $oldIpV6 ]]; then
    echo "$(date): Updating the DNS. Output can be found in ${logfile}"
    echo "$(date): $(curl -k "https://dynv6.com/api/update?token=${token}&zone=${zone}&ipv6=${newIpV6}")" | tee -a $logfile
    echo $newIpV6 > $cachefile
else
    echo "$(date): IP did not Change. Skipping the update" | tee -a $logfile
fi

Use this as a cron job as often as you need and you should be good to go.

I test it on my RPI4b,Which
ip -6 addr show scope global | grep inet6 | sed -e 's/^.inet6 ([^ ])/.*$/\1/;t;d'
will output two AAAA addr,and this script output error like this:
curl: (3) URL using bad/illegal format or missing URL
Sun 05 Feb 2023 09:45:55 AM CST:

can be fix by adding | head -n 1)

can be fix by adding | head -n 1)

Hi there, could you please tell a noob, at which position? I added it behind the URI and it didnt work
dynv6.sh: line 23: ` echo "$(date): $(curl -k "https://dynv6.com/api/update?token=${token}&zone=${zone}&ipv6=${newIpV6}")" | tee -a $logfile | head -n 1)'

Edit: I've read your comment with more care and figured it out. it should be like this:
newIpV6=$(ip -6 addr show scope global | grep inet6 | sed -e 's/^.*inet6 \([^ ]*\)\/.*$/\1/;t;d' | head -n 1)

This is my script (bash), free to use:

#!/bin/bash

bin="curl -fsS"

fqdn=<your_domain>
token='<Your_token>'

ipv4=dig TXT +short o-o.myaddr.l.google.com @ns1.google.com | cut -f2 -d'"'
ipv6=dig -6 TXT +short o-o.myaddr.l.google.com @ns1.google.com | cut -f2 -d'"'

echo "My Ipv6: "$ipv6
echo ""

if [[ $ipv6 =~ ^([0-9a-fA-F]{0,4}:){1,7}[0-9a-fA-F]{0,4}$ ]]
then
echo "Updating $fqdn (ipv6)..."
$bin "http://dynv6.com/api/update?hostname=$fqdn&ipv6=$ipv6&token=$token"
echo ""
else
echo "Invalid IPv6 address"
fi

echo "My IPv4: "$ipv4
echo ""

if [[ $ipv4 =~ ^[0-9]+.[0-9]+.[0-9]+.[0-9]+$ ]]
then
echo "Updating $fqdn (ipv4)..."
$bin "http://dynv6.com/api/update?hostname=$fqdn&token=$token&ipv4=$ipv4"
else
echo "Invalid IPv4 address"
fi

echo "End of DNS records update!"

exit 0
`

`

Here is a node.js implementation of the script, that can be built into an executable with pkg and scheduled using Systemd/Windows Task Scheduler

const os = require('os');

const ip6addr = (os.networkInterfaces())['Ethernet'][1]['address'];
const domain = '<domain>';
const username = '<token>';
const url = `https://dynv6.com/api/update?hostname=${domain}&token=${username}&ipv6=${ip6addr}`;

fetch(url, {
  method: 'GET'
}).then((response) => {
  response.text().then((data) => {
    console.log(data);
  });
}).catch((error) => {
  console.error(error);
});

Like @slyfunky ... I Found my self with a bunch of linux-like scripts...
If you are trying to host with windows, take a look to this repo: https://github.com/slyfunky/Pango/blob/main/DNS.bat

I liked a lot your ideas, like getting dynamically the public ipv4.

Heres is my powershell code:

#!/usr/bin/env pwsh

# Currenty Only support for ipv4.

# zone / hostname
$hostname = $env:SERVICE_HOSTNAME

# HTTP Token got form https://dynv6.com/keys
$httpToken = $env:DYNV6_HTTP_TOKEN

# some service that returns your public ipv4
$publicIpProvider = $env:PUBLIC_IPv4_PROVIDER_SERVICE

if (-not $hostname) {
    Write-Error "The environment variable 'SERVICE_HOSTNAME' is empty. Please set it before running the script."
    exit 1
}

if (-not $httpToken) {
    Write-Error "The environment variable 'DYNV6_HTTP_TOKEN' is empty. Please set it before running the script."
    exit 1
}

if (-not $publicIpProvider) {
    Write-Error "The environment variable 'PUBLIC_IPv4_PROVIDER_SERVICE' is empty. Please set it before running the script."
    exit 1
}

# call to public ip provider
$publicIpProviderResponse = Invoke-WebRequest -Uri $publicIpProvider -ErrorAction Stop

# check the response status code
if ($publicIpProviderResponse.StatusCode -ne 200) {
    Write-Error "Request failed with status code: $($response.StatusCode)"
    Write-Error "Try with other value for PUBLIC_IPv4_PROVIDER_SERVICE"
    exit 1
}

# get ipv4
$ipv4 = $publicIpProviderResponse.Content

# dynv6 http api ipv4 url
$dynv6HTTPApiIpv4 = "https://ipv4.dynv6.com/api/update?ipv4=$ipv4&zone=$hostname&token=$httpToken"

$dynv6Response = Invoke-WebRequest -Uri $dynv6HTTPApiIpv4 -ErrorAction Stop

$dynv6Response.StatusCode